c++ - libssh: 単純な実装で失われたメモリ

Question

非常に単純な実装を試みていますlibsshが、valgrind はメモリリークを示しています。

コードは次のとおりです。

#include <libssh/libssh.h>
#include <stdlib.h>
#include <stdio.h>
#include <errno.h>
#include <string.h>
int main()
{
        ssh_session my_ssh_session = ssh_new();
        int port = 22;
        int rc, state;
        const char *ip = "192.168.125.241";
        char *password;
        if (my_ssh_session == NULL)
                exit(-1);
        ssh_options_set(my_ssh_session, SSH_OPTIONS_HOST, ip);
        ssh_options_set(my_ssh_session, SSH_OPTIONS_PORT, &port);
        rc = ssh_connect(my_ssh_session);
        if (rc != SSH_OK)
        {
                fprintf(stderr, "Error connecting to localhost: %s\n",
                ssh_get_error(my_ssh_session));
                exit(-1);
        }

        state = ssh_is_server_known(my_ssh_session);
        if(state == SSH_SERVER_KNOWN_OK)
                printf("already added\n");
        else
                printf("require addition\n");

        rc = ssh_userauth_password(my_ssh_session, "rohit", "password");
        if (rc != SSH_AUTH_SUCCESS)
        {
                fprintf(stderr, "Error authenticating with password: %s\n",
                ssh_get_error(my_ssh_session));
                ssh_disconnect(my_ssh_session);
                ssh_free(my_ssh_session);
                exit(-1);
        }
        ssh_disconnect(my_ssh_session);
        ssh_free(my_ssh_session);
}

コンパイル:

gcc sshex.c -lssh

VALGRIND 実行:

root@rohit-Precision-T1500:/# valgrind --tool=memcheck --leak-check=full --show-leak-kinds=all --show-reachable=no ./a.out 
==1937== Memcheck, a memory error detector
==1937== Copyright (C) 2002-2013, and GNU GPL'd, by Julian Seward et al.
==1937== Using Valgrind-3.10.0.SVN and LibVEX; rerun with -h for copyright info
==1937== Command: ./a.out
==1937== 
yahoo
==1937== 
==1937== HEAP SUMMARY:
==1937==     in use at exit: 14,256 bytes in 521 blocks
==1937==   total heap usage: 1,339 allocs, 818 frees, 92,442 bytes allocated
==1937== 
==1937== 24 bytes in 1 blocks are indirectly lost in loss record 507 of 520
==1937==    at 0x4C2AB80: malloc (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
==1937==    by 0x56AAD32: CRYPTO_malloc (in /lib/x86_64-linux-gnu/libcrypto.so.1.0.0)
==1937==    by 0x56E3A59: BN_new (in /lib/x86_64-linux-gnu/libcrypto.so.1.0.0)
==1937==    by 0x56E3F07: BN_bin2bn (in /lib/x86_64-linux-gnu/libcrypto.so.1.0.0)
==1937==    by 0x4E6079B: pki_signature_from_blob (pki_crypto.c:1384)
==1937==    by 0x4E599F9: ssh_pki_import_signature_blob (pki.c:1262)
==1937==    by 0x4E59A77: ssh_pki_signature_verify_blob (pki.c:1281)
==1937==    by 0x4E578DE: ssh_packet_newkeys (packet_cb.c:186)
==1937==    by 0x4E56E6F: ssh_packet_process (packet.c:422)
==1937==    by 0x4E57374: ssh_packet_socket_callback (packet.c:326)
==1937==    by 0x4E573B3: ssh_packet_socket_callback (packet.c:336)
==1937==    by 0x4E5D951: ssh_socket_pollcallback (socket.c:290)
==1937== 
==1937== 24 bytes in 1 blocks are indirectly lost in loss record 508 of 520
==1937==    at 0x4C2AB80: malloc (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
==1937==    by 0x56AAD32: CRYPTO_malloc (in /lib/x86_64-linux-gnu/libcrypto.so.1.0.0)
==1937==    by 0x56E3A59: BN_new (in /lib/x86_64-linux-gnu/libcrypto.so.1.0.0)
==1937==    by 0x56E3F07: BN_bin2bn (in /lib/x86_64-linux-gnu/libcrypto.so.1.0.0)
==1937==    by 0x4E607EC: pki_signature_from_blob (pki_crypto.c:1405)
==1937==    by 0x4E599F9: ssh_pki_import_signature_blob (pki.c:1262)
==1937==    by 0x4E59A77: ssh_pki_signature_verify_blob (pki.c:1281)
==1937==    by 0x4E578DE: ssh_packet_newkeys (packet_cb.c:186)
==1937==    by 0x4E56E6F: ssh_packet_process (packet.c:422)
==1937==    by 0x4E57374: ssh_packet_socket_callback (packet.c:326)
==1937==    by 0x4E573B3: ssh_packet_socket_callback (packet.c:336)
==1937==    by 0x4E5D951: ssh_socket_pollcallback (socket.c:290)
==1937== 
==1937== 32 bytes in 1 blocks are indirectly lost in loss record 511 of 520
==1937==    at 0x4C2AB80: malloc (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
==1937==    by 0x56AAD32: CRYPTO_malloc (in /lib/x86_64-linux-gnu/libcrypto.so.1.0.0)
==1937==    by 0x56E35E6: ??? (in /lib/x86_64-linux-gnu/libcrypto.so.1.0.0)
==1937==    by 0x56E3AD4: bn_expand2 (in /lib/x86_64-linux-gnu/libcrypto.so.1.0.0)
==1937==    by 0x56E3ECF: BN_bin2bn (in /lib/x86_64-linux-gnu/libcrypto.so.1.0.0)
==1937==    by 0x4E6079B: pki_signature_from_blob (pki_crypto.c:1384)
==1937==    by 0x4E599F9: ssh_pki_import_signature_blob (pki.c:1262)
==1937==    by 0x4E59A77: ssh_pki_signature_verify_blob (pki.c:1281)
==1937==    by 0x4E578DE: ssh_packet_newkeys (packet_cb.c:186)
==1937==    by 0x4E56E6F: ssh_packet_process (packet.c:422)
==1937==    by 0x4E57374: ssh_packet_socket_callback (packet.c:326)
==1937==    by 0x4E573B3: ssh_packet_socket_callback (packet.c:336)
==1937== 
==1937== 32 bytes in 1 blocks are indirectly lost in loss record 512 of 520
==1937==    at 0x4C2AB80: malloc (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
==1937==    by 0x56AAD32: CRYPTO_malloc (in /lib/x86_64-linux-gnu/libcrypto.so.1.0.0)
==1937==    by 0x56E35E6: ??? (in /lib/x86_64-linux-gnu/libcrypto.so.1.0.0)
==1937==    by 0x56E3AD4: bn_expand2 (in /lib/x86_64-linux-gnu/libcrypto.so.1.0.0)
==1937==    by 0x56E3ECF: BN_bin2bn (in /lib/x86_64-linux-gnu/libcrypto.so.1.0.0)
==1937==    by 0x4E607EC: pki_signature_from_blob (pki_crypto.c:1405)
==1937==    by 0x4E599F9: ssh_pki_import_signature_blob (pki.c:1262)
==1937==    by 0x4E59A77: ssh_pki_signature_verify_blob (pki.c:1281)
==1937==    by 0x4E578DE: ssh_packet_newkeys (packet_cb.c:186)
==1937==    by 0x4E56E6F: ssh_packet_process (packet.c:422)
==1937==    by 0x4E57374: ssh_packet_socket_callback (packet.c:326)
==1937==    by 0x4E573B3: ssh_packet_socket_callback (packet.c:336)
==1937== 
==1937== 48 bytes in 2 blocks are definitely lost in loss record 513 of 520
==1937==    at 0x4C2AB80: malloc (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
==1937==    by 0x56AAD32: CRYPTO_malloc (in /lib/x86_64-linux-gnu/libcrypto.so.1.0.0)
==1937==    by 0x56E3A59: BN_new (in /lib/x86_64-linux-gnu/libcrypto.so.1.0.0)
==1937==    by 0x574C358: ??? (in /lib/x86_64-linux-gnu/libcrypto.so.1.0.0)
==1937==    by 0x5750B1A: ??? (in /lib/x86_64-linux-gnu/libcrypto.so.1.0.0)
==1937==    by 0x5750BC5: ??? (in /lib/x86_64-linux-gnu/libcrypto.so.1.0.0)
==1937==    by 0x5750D79: ASN1_item_new (in /lib/x86_64-linux-gnu/libcrypto.so.1.0.0)
==1937==    by 0x4E60734: pki_signature_from_blob (pki_crypto.c:1347)
==1937==    by 0x4E599F9: ssh_pki_import_signature_blob (pki.c:1262)
==1937==    by 0x4E59A77: ssh_pki_signature_verify_blob (pki.c:1281)
==1937==    by 0x4E578DE: ssh_packet_newkeys (packet_cb.c:186)
==1937==    by 0x4E56E6F: ssh_packet_process (packet.c:422)
==1937== 
==1937== 128 (16 direct, 112 indirect) bytes in 1 blocks are definitely lost in loss record 516 of 520
==1937==    at 0x4C2AB80: malloc (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
==1937==    by 0x56AAD32: CRYPTO_malloc (in /lib/x86_64-linux-gnu/libcrypto.so.1.0.0)
==1937==    by 0x5750D0B: ??? (in /lib/x86_64-linux-gnu/libcrypto.so.1.0.0)
==1937==    by 0x5750D79: ASN1_item_new (in /lib/x86_64-linux-gnu/libcrypto.so.1.0.0)
==1937==    by 0x4E60734: pki_signature_from_blob (pki_crypto.c:1347)
==1937==    by 0x4E599F9: ssh_pki_import_signature_blob (pki.c:1262)
==1937==    by 0x4E59A77: ssh_pki_signature_verify_blob (pki.c:1281)
==1937==    by 0x4E578DE: ssh_packet_newkeys (packet_cb.c:186)
==1937==    by 0x4E56E6F: ssh_packet_process (packet.c:422)
==1937==    by 0x4E57374: ssh_packet_socket_callback (packet.c:326)
==1937==    by 0x4E573B3: ssh_packet_socket_callback (packet.c:336)
==1937==    by 0x4E5D951: ssh_socket_pollcallback (socket.c:290)
==1937== 
==1937== LEAK SUMMARY:
==1937==    definitely lost: 64 bytes in 3 blocks
==1937==    indirectly lost: 112 bytes in 4 blocks
==1937==      possibly lost: 0 bytes in 0 blocks
==1937==    still reachable: 14,080 bytes in 514 blocks
==1937==         suppressed: 0 bytes in 0 blocks
==1937== Reachable blocks (those to which a pointer was found) are not shown.

ダイレクトラン:

root@rohit-Precision-T1500:/# gcc sshex.c -lssh
root@rohit-Precision-T1500:/# ./a.out 
already added
root@rohit-Precision-T1500:/#

Linux バージョン:

root@rohit-Precision-T1500:/# uname -a
Linux rohit-Precision-T1500 3.13.0-43-generic #72-Ubuntu SMP Mon Dec 8 19:35:06 UTC 2014 x86_64 x86_64 x86_64 GNU/Linux

私はこれについて実験しました。関数ssh_connect()（およびもちろん他の次の関数）を削除すると、リークは発生しません。したがって、この関数によってリークが発生したに違いありません。しかし、私の小さなプログラムでは、関数を使用して、ssh_disconnect()によって割り当てられたメモリを解放しましたssh_connect()。では、メモリが確実に解放されていることを確認するにはどうすればよいですか?

私のソフトウェアで SCP 機能を使用したいと考えています。そのため、メモリリークは深刻な問題になるでしょう。libcrypto私の理解によると、リークはおそらくリークではないライブラリに関連付けられていますlibssh。そうである場合、またはそうでない場合、これらのリークを取り除くための解決策は何ですか? 私はどこで間違っていますか？

score 2 · Accepted Answer

と思った通りになりました。これはのバグである可能性がありますlibcrypto。プログラムを実行しましたがRHEL 6.5、valgrind はリークを示しませんでした。

出力のスニペットは次のとおりです。

[root@demo-hadoop test]# gcc sshex.c -lssh
[root@demo-hadoop test]# valgrind --tool=memcheck ./a.out 
==23636== Memcheck, a memory error detector
==23636== Copyright (C) 2002-2012, and GNU GPL'd, by Julian Seward et al.
==23636== Using Valgrind-3.8.1 and LibVEX; rerun with -h for copyright info
==23636== Command: ./a.out
==23636== 
already added
==23636== 
==23636== HEAP SUMMARY:
==23636==     in use at exit: 15,304 bytes in 532 blocks
==23636==   total heap usage: 1,067 allocs, 535 frees, 82,199 bytes allocated
==23636== 
==23636== LEAK SUMMARY:
==23636==    definitely lost: 0 bytes in 0 blocks
==23636==    indirectly lost: 0 bytes in 0 blocks
==23636==      possibly lost: 0 bytes in 0 blocks
==23636==    still reachable: 15,304 bytes in 532 blocks
==23636==         suppressed: 0 bytes in 0 blocks
==23636== Rerun with --leak-check=full to see details of leaked memory
==23636== 
==23636== For counts of detected and suppressed errors, rerun with: -v
==23636== ERROR SUMMARY: 0 errors from 0 contexts (suppressed: 6 from 6)
[root@demo-hadoop test]# 
[root@demo-hadoop test]# 
[root@demo-hadoop test]# uname -a
Linux demo-hadoop 2.6.32-431.el6.x86_64 #1 SMP Sun Nov 10 22:19:54 EST 2013 x86_64 x86_64 x86_64 GNU/Linux

もちろん、これはのバグではありませんlibssh。

c++ - libssh: 単純な実装で失われたメモリ

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